The present invention is generally related to fiber optic networks, and in particular, provides switches for directing optical signals along selected fibers of an optical network.
In fiber optic networks, light signals are transmitted along optical fibers to transfer information from one location to another. Although the propagation of light signals along optical fibers is analogous to the transmission of electronic data along metal wires, transferring the light signals from an input optical fiber to any of a plurality of output optical fibers is somewhat more problematic than the electrical coupling of wires in an electrical switch.
Electrical signals which are sent along a wire naturally propagate between input and output wires when they are electrically coupled together. In contrast, a light signal must be accurately entered into an optical fiber, or much of the signal strength will be lost. Modern optical fibers are very small in cross-section, and typically have a fairly narrow acceptance angle within which light entering the fiber should fall to promote efficient propagation of the light signal along the fiber. Therefore, optical switches generally rely on precise and selectable alignment between one or more input optical fibers and one or more output optical fibers. The alignment requirements of modern single mode optic fibers are particularly stringent, as their core diameters are typically as small as 2.0 to 10.0 .mu.m.
In known electromechanical optical switches, the switching operation is often effected by precise movement of the ends of the input fibers relative to the ends of the output fibers, or by accurately moving a mirror to redirect the optical signals to a selected output fiber without moving the optical fibers themselves. Unfortunately, these accuracy and precision requirements substantially increase the cost and decrease the reliability of known optical switches.
Alternative known optical switch structures split the signal and selectively block the undesired optical pathways. Such switches are highly inefficient, requiring repeated signal amplification. Repeated amplification is costly, and also increases the potential for noise and distortion of the original optical signal. These disadvantages are compounded in complex optical switches which provide multiple alternative pathways with simultaneous switching, such as in 2.times.2 switches, N.times.N switches, N.times.M switches, and the like.
A particular challenge with electromechanical fiber optic switches is that they operate as an interface between two data transmission mediums. While the goal of these structures is to provide switching between optical fibers, they will often be actuated by electro-servos. Hence, when switching failures occur, it may be difficult to determine whether the failure lies in an optical component of the network, an optical component of the switch, an electrical component of the switching control circuitry, or an electromechanical component of the switch itself.
In light of the above, it would be advantageous to provide improved fiber optic switches for use in fiber optic networks. It would be particularly advantageous to provide highly reliable switch structures which provided a long lifetime, but which were more easily manufactured than known switch structures. It would be further desirable to provide such improved switches in a variety of configurations, including 1.times.2, 2.times.2, N.times.N, and M.times.N, with good switching performance, and at an affordable cost.